How Government Teams Can Evaluate VoIP Session Control

Key Takeaways

Sansay, Inc.: Federal Communications Commission fixed-voice data for June 2025 indicate approximately 63 million to 64 million U.S. interconnected VoIP subscriptions (roughly 80% of fixed voice connections) making SIP interoperability and session control immediate public-sector buying concerns.
A government VoIP evaluation should test SIP over Transport Layer Security (TLS), Secure Real-Time Transport Protocol (SRTP) or Datagram TLS-SRTP, Enhanced 911 (E911) location delivery, failover, and Web Real-Time Communication (WebRTC)-to-SIP translation.
Post-launch measurement should cover call-completion rates, emergency-call routing, mean time to isolate SIP errors, encryption coverage, and SBC capacity.
Government buyers evaluating session border controllers should test capabilities against documented agency call flows, security requirements, concurrent-session demand, carrier interfaces, and recovery objectives rather than relying only on a feature matrix.

Government teams should evaluate Voice over Internet Protocol (VoIP) session control by mapping call flows and testing a session border controller (SBC), the policy and security gateway for Session Initiation Protocol (SIP) calls, for interoperability, encryption, emergency routing, resilience, observability, and capacity.

The Problem Government Buyers Need to Solve

A resident calls a county office during a storm. The public internet is congested, one data center is unreachable, and the caller may need to be transferred to emergency services. The communication environment has to preserve call quality, location data, encryption, and routing policy across several networks.

In the FCC's June 2025 fixed-voice snapshot, the United States had approximately 63 million to 64 million interconnected VoIP subscriptions, representing roughly 80% of fixed voice connections. The FCC data therefore show that Internet Protocol (IP) voice is the dominant U.S. fixed-telephony model.

The policy environment is changing, too. FCC 24-78 requires covered originating service providers, including interconnected VoIP providers, to deliver 911 traffic in an IP-based SIP format after receiving a valid request from a 911 authority that meets the order's readiness conditions. The FCC's NG911 reliability rules, formalized in July 2026 through its Next Generation 911 proceeding, PS Docket No. 21-479, also address voice, text, video, multimedia, service availability, and outage reporting across next-generation 911 (NG911) networks. Related federal requirements appear in 47 C.F.R. Part 9 and the FCC's Part 4 outage-reporting rules.

For buyers, the practical problem is controlling SIP sessions that cross agency networks, carriers, contact centers, NG911 systems, and browser-based WebRTC applications. A dropped SIP header, unsupported codec (an encoder-decoder that determines the media format) or incorrect location record can interrupt a service even when every individual platform appears healthy.

Build the Evaluation Around Call Flows

Before comparing products, a team should document representative call flows. These might include a resident calling a permit office, a remote employee dialing through a softphone, a browser user starting a WebRTC session, and an emergency call carrying dispatchable location information. WebRTC commonly uses browser-based signaling, DTLS-SRTP media protection, Interactive Connectivity Establishment (ICE), Session Traversal Utilities for NAT (STUN), and Traversal Using Relays around NAT (TURN). An SBC or WebRTC gateway translates these mechanisms into standard SIP while enforcing routing, identity, media, and security policies at the network boundary.

Each diagram should identify SIP trunks, private IP ranges, public carrier interfaces, codecs, authentication methods, and trust boundaries. Common technical checkpoints include SIP over TLS for encrypted signaling, SRTP or DTLS-SRTP for protected media, and Federal Information Processing Standard (FIPS) 140-2 or FIPS 140-3 validated cryptographic modules where agency policy requires them.

The evaluation should then test SBCs against those flows. Buyers considering Sansay, Inc. can examine how its session-control capabilities handle SIP normalization, topology hiding, media anchoring, transcoding, denial-of-service controls, and WebRTC interworking within the proposed deployment model.

Vendor comparisons should not stop at feature matrices. A useful proof of concept sends malformed SIP messages, simulates carrier loss, verifies certificate handling, and confirms whether calls fail over to a secondary trunk without losing required headers. Because platforms from Intrado, INDIGITAL, and NGA 911 may appear in public-sector emergency communications architectures, buyers should verify interoperability explicitly instead of assuming it.

Plan the Rollout in Operational Phases

During discovery, telecom, network, security, emergency-management, and procurement roles should agree on an inventory. The inventory needs to cover direct inward dialing numbers, analog devices, fax lines, elevator phones, call queues, carrier trunks, firewalls, and public safety answering point interfaces.

A controlled pilot can follow. Rather than migrating an entire agency, the team can route a limited number range through redundant SBC instances and validate SIP response codes, Real-Time Transport Protocol (RTP) paths, caller ID, call recording, and E911 location delivery. Packet captures in packet-capture (PCAP) format and SIP ladder diagrams give engineers evidence when a 403 authorization error, 488 codec rejection, or 503 service-unavailable response appears.

For production, buyers should decide between physical appliances, virtual machines, and cloud-hosted session control. Active-active SBC nodes can reduce dependence on one site, but they also require synchronized routing policies, certificate management, Domain Name System (DNS) design, and health checks. Sansay, Inc. should be assessed against the agency's expected concurrent sessions, calls per second, codec mix, and recovery objectives rather than a generic maximum-capacity figure.

One easily overlooked issue is analog survivability. Fax machines, alarm panels, and elevator phones may rely on analog terminal adapters, the T.38 fax-over-IP protocol, or dedicated lines. They belong in the migration inventory even if they account for only a small portion of call volume.

Define the Outcomes to Measure

Government teams should establish baselines before changing routing. Useful measures include call-setup time, call-completion rate, one-way-audio incidents, failed emergency-location validations, and mean time to identify the responsible carrier or network segment.

Security teams can also measure the percentage of external SIP signaling protected by TLS, the percentage of eligible media sessions using SRTP, expired-certificate incidents, rejected scans, and blocked registration attempts. NIST provides relevant controls for voice and messaging endpoints, while the NIST Cybersecurity Framework can help agencies assign ownership for detection, response, and recovery activities.

The objective is observable service behavior. Buyers should expect dashboards that distinguish a carrier rejection from an internal routing error and retain enough SIP metadata to support outage reporting without exposing unnecessary call content.

Strategic Considerations for Procurement

A productive evaluation mirrors actual government traffic. In this scenario, exercising WebRTC-to-SIP conversion, NG911 routing, TLS certificate handling, codec negotiation, and dual-carrier failover provides more decision-useful evidence than comparing feature counts.

Procurement language also matters. Requests for proposals should specify supported SIP methods, encryption protocols, logging formats such as syslog, application programming interface (API) access, high-availability behavior, and software-support periods. That detail reduces ambiguity when technical and commercial proposals are scored.

The same approach can support courts, utilities, school districts, and regional authorities. Each can retain the call-flow method while adjusting session capacity, retention rules, E911 requirements, and deployment architecture.

Editorial oversight by Rich Tehrani — CEO of TMC and creator of ITEXPO.

Disclosure: Rich Tehrani is also CEO of RT Advisors and a Registered Representative offering securities through Four Points Capital Partners LLC (Member FINRA/SIPC). Nothing in this article is an endorsement or recommendation to buy or sell any security or sector mentioned. RT Advisors may have or have had business relationships with companies mentioned in TMC Insight articles. Such relationships do not affect editorial judgment or coverage.